This invention relates to an apparatus and method for treating of oil or gas wells for corrosion, removal of paraffin deposits and the like.
One of the problems commonly encountered in the producing oil well is the corrosion of the well tubing and the plugging of the tubing with paraffin, a mixture of heavy hydrocarbons with a relatively high melting point. Corrosion or deposition of paraffin is a gradual process which can eventually clog or create holes in the tubing. It will result in loss of production unless the corrosion and paraffin is removed.
One common method to remove paraffin buildup is to use a well pump to pump hot oil down the casing annulus of the well. The hot oil goes down through the casing annulus all the way to the well pump and is pumped to the surface through the tubing. The hot oil tends to melt the paraffin, so that it is pumped up and out of the well.
Corrosion is traditionally treated by a similar process. However, instead of hot oil corrosion inhibitors are pumped down the casing annulus all the way down to the well pump and then are picked up by the well pump and carried back to the surface through the well tubing. The corrosion inhibitors are designed to coat the inside of the well tubing to prevent corrosion of the tubing in highly corrosive environments, such as water, salt water, acid and/or corrosive gas such as carbon dioxide or hydrogen sulfide.
Since the pump is a rod and/or pump lift system is located at the bottom of the tubing and acts as a plug in the bottom of the tubing. The commonly used procedures described above for treatment of a well for corrosion and paraffin deposit buildup are both time consuming and expensive. In the treatment for paraffin buildup, for example, a large amount of oil has to be heated by a special device on location to a temperature high enough to melt paraffin before it is pumped into the well, so that the oil is still hot enough to melt paraffin when it reaches the well pump and well tubing. A typical hot oil treatment of a typical well under present methods could require up to one hundred barrels of oil heated to 300 degrees fahrenheit. In addition to the heating cost of heating such a large amount of oil to the required temperature, there is also great economic costs involved due to cutting off production of the particular well during the time required to treat the well with hot oil and during the time it takes to recover the oil. The amount of time lost depends on the production rate of the well and the time lost can be up to several days for a slow producing well. For instance, if 100 barrels of hot oil are required under present methods to treat a well that normally produces at the rate of 50 barrels a day, the treatment will require the loss of two days of production while the hot oil that was pumped downhole is being pumped out.
For similar reasons treatment of a well for corrosion requires considerable expense. Under present methods, corrosion inhibitors coat metal surfaces with a layer of protective material to prevent attack of the metal by corrosive liquids. The corrosion inhibitors are pumped into the casing. At the bottom some of the chemicals are picked up by the well pump and are pumped out through the tubing, though much of the expensive corrosion inhibitors are lost in the casing and are not recovered by the pump.
One could easily appreciate the deficiencies of the common method of well treatment through the casing, when only a particular part of the tubing, mainly above the well pump, requires treatment. By using the current methods, most of the well treatment fluid is wasted and not recovered.
Such problems led to the creation of various devices which enable a user to pump oil directly through the tubing, so that the treatment fluid reaches the part of the well tubing that has to be treated, instead of being wasted in the casing annulus. This arrangement not only saves on the amount of treatment fluid, but significantly reduces the time required to treat the well, thus saving on production costs and directly effecting the productivity of the particular well.
Various devices have been offered to allow treatment of the wells directly through the tubing. Some of these devices utilize valves which are spring-operated. However, numerous field tests showed that at high pressure applications the springs tend to break, which defeats the purpose of the valves and causes to spend valuable time to repair or substitute the malfunctioning device.
The present invention contemplates provision of a treating valve and method to enable: 1. treatment of wells even at high pressure and 2. by allowing to pump a treatment fluid through the tubing.